SCHMAEMAN, C.N.*; MENDON�A, M.T.; Auburn University, Auburn, AL; Auburn Univsersity, Auburn, AL: Preliminary Study: Seasonal and Sex Differences in Immunocompetence in Hibernating Big Brown Bats

There is little known about the consequences of hibernation on immunocompetence in vertebrates. The immune system is known to be sensitive and responsive to environmental changes as well as hormonal and nutritional factors. We conducted a preliminary study on the seasonal changes in immune responsiveness in a captive colony of male and female big brown bats (Eptesicus fuscus). From 2002-2003, the bats were housed in environmental chambers that allowed us to alter the temperature and photoperiod. Bats were kept on a natural photoperiod cycle. During Dec. � March, bats experienced alternating periods of 5 degrees C for 7 days and then 22 degrees C for 5 days. This manipulation mimicked the natural cycle of torpor and arousal found in bats in the southeastern US. We used two assays to access immune response. A phytohemagglutinin (PHA) skin test was used to assess T-cell responsiveness and sheep red blood cells (SRBC) were used to assess B-cell responsiveness. The assays were administered before and during the torpor period. There were no significant differences in the T-cell response between the seasons or the sexes. We did observe significant differences in B-cell response: before hibernation females responded faster then males while during hibernation, males responded faster then females. Both sexes had a higher peak response in non-hibernating then hibernating conditions.